dressing rooms barely exist anymore. test drive memes are usually for specific games, as a means of trying out the setting, but you can play on them without worrying about joining. the best bet is bakerstreet or poking around rpanons or enablemeplz to request psls if you're not interested in any games.

if you are looking into games, there's a directory for the ones that are currently open. https://dwrpmasterlist.dreamwidth.org/ and you can check the game ads on rpanons for things that have opened recently or are advertising.